Ligament and tendon replacement in mammals has long sought a material that approximates the load transmission and performance of the native ligament and tendon structures. Synthetic ligaments and tendons have been made from steel, polyester, polyurethane, polyethelene, Nylons, polytetrafluoroethylene, carbon fiber and other man made materials. Combinations of any one or more of the aforementioned materials have also been used to manufacture synthetic ligament tissue. However, synthetics typically experience decreasing functional capability over time, and can wear out, fray and/or particulate in relatively short time periods (e.g. about, 1, 2, 3 or 4 years) after implantation.
As an alternative to synthetic materials, natural ligament or tendon tissue harvested from a donor site, such as autografts and/or cadaveric tissue grafts (i.e. allografts), may also be used in ligament or tendon replacement procedures. As with synthetic materials, for both autografts and allografts, long-term recovery of functional parameters (e.g., failure load, linear and tangential stiffness, failure stress, and strain at failure) remain significantly reduced compared to native ligament, tendon or other soft tissue structures.
Autografts come from donor sites of the recipient of the graft itself. For example, in ACL (anterior cruciate ligament) reconstruction, a part of the patient's own patellar ligament or hamstring tendon can be used to replace the torn ACL.
A cadaveric tissue graft can be placed in the site of the torn ACL, for example, without donor site morbidity associated with autograft harvesting. Although cadaver tissues are typically treated in some way to reduce any foreign body reactions, they can transmit disease. In most cases allografts heal more slowly and tend to have significantly higher failure rates than autografts.
Man made and cadaveric tissue grafts are advantageous over autografts because they do not have donor site morbidity and pain, both immediate and long-term, associated with harvesting autografts.
Accordingly, there is a need for a material for ligament, tendon and other soft tissue repair and replacement that is free of donor site morbidity associated with autografts, has improved failure rates over traditional allografts and synthetic tissues, and better approximates native tissue biomechanical performance.
The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known, or part of the common general knowledge as at the priority date of any of the claims.
Throughout the description and claims of the specification the word “comprise” and variations thereof, such as “comprising” and “comprises”, is not intended to exclude other additives, components, integers or steps.